Many applications of analog circuits require stable, predictable current references. These applications may include, but are not limited to, sensing and amplification circuits, signal converters, signal conditioning circuits, programmable reference signals, signal comparators, temperature controlled clock generators, temperature controlled delay circuits, function generators, noise generators, measurement systems, power optimization and protection circuits. In some applications, predictability translates to a circuit which produces a constant voltage or current over time, temperature, process variations, etc.
Not all applications require stringent immunity to environmental and process parameters, but may require only a predictable variation with a given parameter. For example, an application may require currents that vary over temperature in a predictable way, such as a current reference with a positive, linear slope versus increasing temperature. The related art includes devices that employ independent circuits for producing proportional to absolute temperature current references, constant (i.e., zero temperature coefficient) current references, and complementary (i.e., negative slope) to absolute temperature current references, respectively. Still other related art current references may be based on multiple resistors having different temperature coefficients.
Unfortunately, related art current references generally do not provide for temperature slope control or may suffer from large size and power inefficiencies due to their complexity or suffer from high sensitivity to process variations.